1. Field of the Invention
The present invention relates to a semiconductor device, and particularly to a semiconductor device provided with leads which bend in a thickness direction.
2. Description of the Related Art
Generally, a semiconductor device using a lead frame is provided with an island and multiple leads each having one end mounted around the island. On the top surface of the island, a semiconductor element is fixed, and bonding pads on the semiconductor element are bonded to the leads with thin metal wires. This technology is described, for instance, in Japanese Patent Application Publication No. 2007-5569. Furthermore, the island, the leads, the semiconductor element and the thin metal wires are sealed with an insulating resin so that the end portions of the leads may be exposed to the outside. Here, the portion of the lead sealed with the insulating resin is called an inner lead, and the portion of the lead exposed from the insulating resin is called an outer lead. The outer lead is bent as necessary, so that the other end of the lead is mounted on a printed board with solder, for example.
Moreover, a stacked semiconductor device is also fabricated by stacking multiple chips on an island. This is made by stacking a parent chip with a child chip smaller than the parent chip. The parent chip and also the child chip are electrically bonded with a thin metal wire.
With reference to FIG. 11A to 11C, description will be given specifically of a configuration and the like of a conventional semiconductor device 100. FIG. 11A is a plain view of the semiconductor device 100 as viewed from the above. FIG. 11B is a cross-sectional view of the semiconductor device 100 taken along the line B-B′ of FIG. 11A. FIG. 11C is a cross-sectional view for describing a wire-bonding step.
As shown in FIG. 11A and FIG. 11B, the semiconductor device 100 includes: an island 104; leads 102A and the like; a semiconductor element 106 which is fixed to the bottom surface of the island 104; thin metal wires 108 which electrically bond the semiconductor element 106 to the leads 102A and the like; and a sealing resin 120 which integrally seals these constituents.
As shown in FIG. 11A, the island 104 is disposed on the center of the semiconductor device 100. In FIG. 11A, a lead 102B (suspension lead) is projected to the outside from a side surface on the upper side of the island 104, and a lead 102E is projected to the outside from a side surface on the lower side of the island 104.
Each one end of the lead 102A, a lead 102C, a lead 102D and a lead 102F is disposed around the island 104. Each other end thereof is projected to the outside from the sealing resin 120. The bottom surface of the one end of, for example, the lead 102A is bonded, via the thin metal wire 108, to an electrode on the semiconductor element 106 which is fixed to the bottom surface of the island 104.
As shown in FIG. 11B, the lead 102F includes a bonding portion 118, an exposure portion 114 and an inclined portion 116. The bottom surface of the bonding portion 118 is bonded to the thin metal wire 108. The end portion of the exposure portion 114 is exposed to the outside from the sealing resin 120. Both of the bonding portion 118 and the exposure portion 114 are connected to each other while sandwiching the inclined portion 116 configured to incline and extend therebetween. Such a configuration is also employed in other leads. Furthermore, the bonding portion 118 of the lead 102F is positioned on the same plane as the island 104.
By providing the lead 102F with the inclined portion 116 as described above, it is possible to dispose the semiconductor element 106 and the thin metal wire 108 in the space below the island 104, and thereby the entire device is made thin.
As shown in FIG. 1C, the thin metal wire 108 is formed by using a capillary 116. Specifically, firstly, the capillary 116 is moved to the electrode formed on the top surface of the semiconductor element 106 so as to bond the thin metal wire 108 to the electrode. Subsequently, the capillary 116 is moved to the top surface of the bonding portion 118, and the thin metal wire 108 is fixed thereto. Thereafter, the thin metal wire 108 is cut off.
However, as shown in FIG. 1C, when the thin metal wire 108 is bonded to the bonding portion 118 of the lead with the above-described configuration, there is a problem that it is difficult to perform the wire-bonding. Specifically, in order to bond the thin metal wire 108 to the top surface of the bonding portion 118 of the lead 102F, the thin metal wire 108 needs to be pressed and fixed to the top surface of the bonding portion 118 with the lower end of the capillary 116. Nevertheless, in order to reduce the size of the entire device, the area of the top surface of the bonding portion 118 is made small as compared to the width of the capillary 116. For this reason, when the capillary 116 is made to approach the bonding portion 118, the end portion on the right side of the capillary 116 is brought into contact with the inclined portion 116. Accordingly, there is a problem that the inclined portion 116 of the lead 102F is deformed by the contacting impact with the capillary 116.
Furthermore, the semiconductor device configured as described above can be reduced in size by the miniaturization technique in these days. However, the top surface of the child chip is disposed on a higher position above the surface of the island than that of the parent chip. Accordingly, there is a problem that the thickness of the semiconductor device, that is, the thickness of the package is increased, as the top portion of the thin metal wire is further elevated by bonding the thin metal wire to the top surface of the child chip.